The error happens when:

We upload and enable a custom rule => the custom rule must be fired during the analysis
We enable the option "Export CSV"
We enable the option "Allow network access"

The combination of those 3 things causes an exception in Windup while doing the analysis. I also discovered that this bug happens in both:

"OCP deployment" and
the "Web Console (the one we run on our laptops)"

I took my time to also do the same analysis with the stable version 5.2.1.Final and the same bug appeared.

The steps to reproduce the ticket are:

Create a Project and upload customers-tomcat-0.0.1-SNAPSHOT.war
Upload a custom rule custom-rule-example.windup.xml
Select EAP 7 as a target
In the advanced options enable "Export CSV" and "Allow network access"
Run the analysis and it will fail